How did they know during Apollo how much radiation shielding was needed for their spacecrafts and their space suits? They are not even sure today how much shielding they will need on the return to the moon. I've read here that the Apollo astronauts were not in the Van Allen belts very long so they did not receive much exposure. But on the moon which is radioactive they were exposed to cosmic rays, solar radiation, x-rays, gamma rays, beta rays, protons, neutrons for days. Why didn't any of the Apollo astranouts get sick from the radiation?